This invention relates to mesh structures such as those used for cargo restraint nets, and to methods for the manufacture of such mesh structures.
Cargo restraint nets are used in many different shipping and transportation applications to prevent undesired shifting of cargo. Such netting is typically made from a high strength mesh structure which may be formed from any of numerous suitable materials and processes. Among the materials commonly used for such nets are synthetic fibers, such as coated polyesters, multi-filament polypropylenes, nylons and mixtures thereof, which are formed into elongated members or strands. These strands are then used to create a mesh structure by various methods such as weaving, knitting, rochelle, or weft insertion.
One technique used to form mesh is to knot the warp and weft strands together at their points of intersection. This, however, results in an inherent weakness at the knots due to stress concentrations. In cases where the strands are made of synthetic material, it is also known to bond the warp and weft strands together at the intersections by heat or chemical welding. Welding of synthetic strands can also lead to weakness at the joints.
U.S. Pat. No. 4,000,344 teaches a netting formed by threading each strand through a hole formed in the other strand at the intersection point. After completion of this weaving process, the net may be impregnated with a binding agent to cause the synthetic fibers of each strand to cohere, thereby promoting the non-slip quality of the intersections.
It is known that some types of synthetic materials, such as thermoplastics, shrink when heated to a temperature below the melting temperature of the material.
In carrying out this invention in the preferred embodiment described and depicted herein, a mesh structure comprises first and second sets of intersecting elongate members, referred to as weft strands and warp strands respectively. The warp strands are knitted or woven from threads formed from synthetic fibers which shrink when heated, and the weft strands pass through the weave of the warp strands at the points of intersection, hereinafter referred to as xe2x80x9cnodes.xe2x80x9d Heat is applied to the mesh structure to shrink the weave of the warp strands tightly around the weft strands at the nodes, thereby co-joining the weft and warp strands to form a high-strength mesh.
In a preferred embodiment of the invention method for producing a synthetic mesh, the mesh is heated by exposing it to the rays of an ultraviolet lamp. The ultraviolet heating can be precisely controlled in both intensity and time of application, so that the warp strands may be heated just enough to achieve the desired amount of shrinkage without melting either the weft or warp strands.